Mobile communication systems operate on a cellular basis in which transmission and receiver base stations coupled to a network provide transmission and reception to user equipment (UE) such as mobile telephones in each cell in a network. There is usually a single base station in each cell. The base stations themselves are usually referred to as macro base stations and the cells as macro cells.
Smaller cell sites called Pico cells have been proposed. These cover a smaller area such as a complex of buildings. Still smaller cell sites named FEMTO cells are also proposed. This is a term used by mobile operators to refer to cell sites of the type which attempt to solve the often expensive problem of providing complete in building coverage. PICO cells can have problems with low or multi-path distortion etc when they are used to provide coverage to a complete building.
A FEMTO cell is often referred to as an access point/home gateway. It is a small plug and play device which communicates with user equipment such as mobile handsets using standard 2G or 3G transmission reception. It is connected to the celluar network via a broadband service using either Xdsl (digital subscriber loop) or Wimax Technology. Optionally a FEMTO cell can incorporate the functionality of a broadband router so that a user has a completely integrated device. It is of course essential that it integrates seamlessly with the core network of the mobile communication system so that it can be remotely managed and updated.
These access points have limited bandwidth and therefore are only able to cope with a limited number of connections from mobile communication devices before the band width is exceeded. Thus, for example, an access point may have a capacity of ten voice calls which it may handle simultaneously. It is therefore possible that access points can quickly reach their capacity in terms of the calls they can handle and when this happens other users are not able to make calls.
It will be appreciated that it is necessary for an access point to be able to support emergency calls. This is because when an emergency call is made it is important that a user of a mobile communication device can advise the emergency services of his location. As FEMTO cells are deployed in an unregulated and uncoordinated manner, the knowledge of the location of a particular FEMTO cell in which a user is located will not be information which is known to the network and therefore it is important to speak to the person reporting an emergency.